How Light and shadow affect colors?

[Drl]

Dear Krita art community, i apologize for interrupting you again with my art questions, but i am begging for answers once more.

I am going INSANE trying to find answers to my questions. Like always.
And i really want to solve this one artistic mystery that keeps on making me mad (and sad) [and confused] {and ready to die}

Can someone straight on say: what’s the realistic relation between light color and shadow color? And what saturation the light and shadow posses, and how the saturation of light affects the shadow (or vice versa)?

Every little thing i THOUGHT i knew was just dashed away, and the answers slip my mind. Having drawn multiple pictures, i have never been more curious after looking at how light is used in this post: https://www.instagram.com/p/CJdl5Sfh8N7/
I’m looking at how the light-color affects the rest of the shadows and colors on the pieces, and frankly it doesn’t make sense in my head even though it should, shouldn’t it? All i know is that it looks right, but i wonder - why?

Here’s some things i THOUGHT were true, before realizing they don’t explain the light usage in that post. Here’s some rules i THOUGHT were real. That i THOUGHT i could use one day to touch realism:

1. I thought, if there are two light sources, the shadow is a color that’s a mix of the two lights (as in, in sunlight, the weaker sky-light gets into the shadows, making them cold/blue, the yellow from the sun preventing total blue-ness, maybe going a bit purple?)

2. I also thought, lights have shadows that are color opposites (cold light - warm shadow, warm light - cold shadow)
   

   
   
   or just making it darker by going towards the opposite color
   
   

3. Subsurface scattering was a thing only with warm/red light on skin since it’s red(or something like that)https://th.bing.com/th/id/R9aa533b6f48422e58f8bb7152582cad0?rik=yICfPLtjjOqkIQ&pid=ImgRaw

4. The CMYK lights can intensify the color or desaturate it (blue on blue = more intense blue, red on blue = less intense blue, maybe even purple midtone?
   since green=cyan+yellow, if you shine a green light on a non-cyan-or-yellow object, it will look duller)
   

   

5.the mid-tone is more saturated when it’s the same light hitting the same colored object
6. Saturated lights = desaturated shadows (and vice versa, again, maybe?)
7. The darker something is, the harder it is to see color variation of the OBJECT because the OBJECT gets covered by the color/temperature of the LIGHT (as color is just material with light on it, so the lack of light would take that color clarity a bit)
8. Light bouncing off of objects changes color, borrowing it a bit from the object they bounce off of

So yeah. That’s a bunch of contradicting statements, if i ever seen any!

Because putting this all together, i cannot explain how the light in the instagram post works. Or in some realistic artworks, too! And looking at how the light is used there, it looks correct. And even with all my rules, i cannot explain it. I cannot. because i’m too stupid for it

I appreciate whoever read this far! I would love nothing more than to know how wrong i am, or which one of the rules i learned is incorrect! I’m so sick of coming back to this topic! and failing in realistic lighting, which i am trying to understand and i fail every time. (i’m trying to figure out the rules because reference-study doesn’t teach me anything, it never did)

If you think i had all the rules SO TOTALLY WRONG i shouldn’t be an artist, i would appreciate if you told me, too. God knows i need to know if i should give up sooner rather than later - Judge my entire art-page, if you want to https://www.deviantart.com/darkrooklobby/gallery/all

That’s all. I’m so confused, i am 100% missing something crucial, and i am dying trying to figure it out, my art teachers are not helping
art videos are not helping
looking outside stopped helping

this will forever bother me

[wojtryb]

To understand how the colors really work you need to start with how humans perceive it.

In your eyes there are intensity detectors (which we don’t need here), and three types of color detectors called cones (which we need very much). Those three will turn on respectively on short, medium and long light. Those are respectively blue, green and red.

You eyes can detect only those three, so all the others need to be interpreted by your brain as a combination of those three. Only blue cones activated make your brain render object as blue, but blue and green will be displayed as cyan. Green + red = yellow. Blue + red = purple (those combinations of the two can be seen on a color wheel). All the three cones activated are white, none of them is black.

Now you have a basic idea how you interpret a light from light source. Lets add a object reflecting light. In fact “local color” of an object, so how you would normally call it, depends on how good it is at reflecting specific wavelengths. We start with sunlight (which is white - it contains the whole spectrum between red and blue)

In this example with white light, you have four boxes, each being hit by the light of all the lengths. “Green” box is able to reflect only the green (middle) light. The rest goes into it (will just make it hotter, but you don’t need this info).

“White” reflects everything that hits it. Purple will reflect red and blue and absorb green (exact opposite of green light - those are called complementary colors, and our brains kind of like them together, but that’s more of a preference than a science rule). At last, you also have “black” box that absorbs nearly all the light, so it the same as if you had no light in your scene.

If that’s clear, lets move on to colored light. I took the same scene and lit it with green light. This means there are no other wavelengths than middle ones. White and green becomes impossible to distinguish. They both are good at reflecting this type of light, but you have no information how good they are at reflecting blue or red. The same goes with the next two - you only have info that those boxes won’t reflect green, but you can’t know that the third one would do well with red and blue, while the fourth, not at all.

How to use this in practice? Usually you have just one light source in a scene - sun, but it gets split into two - diract and ambient light. If an object is hit directly by the sun, you can say it’s in white light. If not - it’s in the shadow - it should be perfectly black. It would actually be in space, but not on earth.

The air is an object itself, and it’s very good at scattering blue (short) light. This means red and green light goes straight, while blue light comes from all the directions. Long story short - everything in shadows gets only faint blue light, so the objects get bluer if they can reflect blue light. (In the example - blue ambient light from the sky + white sunlight - something you could expect from a shiny day).

Of course there are many more examples and cases here - cloudy day means light gets scattered in clouds, and you get dim gray instead of blue (grays are also a combination of all the frequencies, but just less of each one. In general color lightness is just a weighted sum of all the light rays).
Then you should also think about reflected light as of a light source itself. Light that got reflected hits not only your eyes, but also nearby objects. You can see this in the picture below - green object reflects green light from the white light all around. This green light hits a shadow of a white (reflective) box, and makes this box look green even with non-colored ambient.

This effect is especially visible in forest scenes, where everything is good at reflecting green, so that the shadow turn green instead of blue.

Now moving on to this instagram post you mentioned. Skin of this character is “white” - it reflects everything. It’s a little better with reds, which makes it pink-ish but still.
Second picture is sunset light probably - light got yellow/red (too much explaining for now), with purple ambient (mostly artistic choice, but could be achieved with purple room).
Third picture is a person illuminated in a red room. Fifth is done with two light sources. in a purple room. As the character is white, it reflects nicely both this cyan light from right and red light from left.

I hope this clears things a little bit. I started working on yt tutorials about light (from start to finish), but took a break as the interest was very weak I’ll post this first episode though.

The Sun - Light theory (Pt.1) || course for artists

Cheers

[wojtryb]

Trying to answer your questions fast:

1. With two sources, I hope it should be clear now - if sth is lit with just one, you lit object with one color of light (like only red). If both hit it (red and blue), they merge (that would be purple/pink). If none of them hits object - use ambient color (green here)
   

   

2. Don’t like this rule - it often happend as usually you have white light and blue ambient which makes shadows bluer (and people call blue a cold color)
   Example probably uses a yellow light and blue light as this “looks well”, but it’s doesn’t have to be like that. Can’t tell if your paintings are correct without background that would specify the hue shift of shadows - red and blue balls look bad with such a black shadow (like there is just void out there and that never happens). Brown ball looks nicer with bluer shadow that tells there’s a blue sky above or sth - still no background though.

3. skin contains red blood. If you have a thin organic object like ear, the red light from behind would go trough.

4. No idea - cmyk is only for printing.

5. No idea I’d use the green light example from post above
   6.I never found an always true rule about realistic saturation. I’d use saturation to make specific parts pop out when it gets hit by strong light it can reflect and would use less saturated colors for shadows. But it’s more of artistic choice and making things work out.

6. Dark objects just reflect a very small amount of light. Dark blue means it’s bad at reflecting all the lengths, but blue is the best (though still quite bad). Then the problem is that blue saturates only in dark, while yellow only in light…
   The answer here would be that your brain searches for big contrast areas first, so you won’t notice that much color variations in the dark shadows.

7. The whole post above explains how it work

[Drl]

Thank you very much!

[Drl]

So amazing, you are so helpful!
I’m so happy you decided to help me out, you have no idea. I learned a lot. Now i just need to remember your 2 responses and attempt to apply them
(I will try my best to study this~)
I bet your explanations and videos will help many more lost artists like me. Thank you very much!